A cooling fan is very important to a computer and peripherals thereof because it directly influences the operating performance and stability and the service life of the central processing unit (CPU) and relevant internal components of the computer and other peripherals. The cooling fan is usually designed to meet the requirements of low operating vibration, low operating noise, high heat dissipation efficiency and long service life. In response to the present trend of reduced computer dimensions, the cooling fan therefor now also has small and compact design as well as low power consumption.
FIG. 1 is a sectional view of a conventional cooling fan, which generally includes a base 10, a stator 11 and a rotor 12. The rotor 12 includes a shaft 121 and an oil-impregnated bearing 122 that are rotatably assembled to each other to constitute a rotation support structure of the rotor 12. For the shaft 121 to maintain stable and smooth rotation, the oil-impregnated bearing 122 must be able to stably hold the shaft 121 therein. That is, how the oil-impregnated bearing 122 is mounted has important influence on the operating stability of the rotor 12. When the cooling fan operates, the shaft 121 spins quickly in a shaft hole 1221 of the oil-impregnated bearing 122 and brings the lubricant oil pre-filled in the bearing 122 to move forward along the shaft 121. This condition causes the lubricant oil in the bearing 122 to gradually decrease with time and eventually result in loss of oil from the bearing 122. The decrease or loss of the lubricant oil would inevitably lead to an increased friction coefficient between the shaft 121 and the oil-impregnated bearing 122 and accordingly high operating temperature of the cooling fan, which all have adverse influence on the smooth rotation of the fan to shorten the service life thereof.
In brief, the conventional cooling fan design has the following disadvantages: (1) shortened fan service life; and (2) increased fan maintenance cost.
It is therefore tried by the inventor to work out a way to overcome the above disadvantages of the conventional cooling fan design.